Extract Syntax highlighting from TextEdit and add EditorSyntaxHighlighter

- Extacted all syntax highlighting code from text edit
- Removed enable syntax highlighting from text edit
- Added line_edited_from signal to text_edit
- Renamed get/set_syntax_highlighting to get/set_syntax_highlighter
- Added EditorSyntaxHighligher

modules/visual_script/visual_script_editor.cpp

@@ -4660,10 +4660,10 @@ void VisualScriptEditor::_member_option(int p_option) {
 	}
 }
 
-void VisualScriptEditor::add_syntax_highlighter(Ref<SyntaxHighlighter> p_highlighter) {
+void VisualScriptEditor::add_syntax_highlighter(Ref<EditorSyntaxHighlighter> p_highlighter) {
 }
 
-void VisualScriptEditor::set_syntax_highlighter(Ref<SyntaxHighlighter> p_highlighter) {
+void VisualScriptEditor::set_syntax_highlighter(Ref<EditorSyntaxHighlighter> p_highlighter) {
 }
 
 void VisualScriptEditor::_bind_methods() {